FIELD OF THE INVENTION
This invention relates to a process for treating rendering plant type wastes. The term "rendering plant" is used to refer to those industrial facilities which are engaged in the killing and/or processing of animals, fish, poultry, dairy products and the like.
Various types of proteinaceous refuse are produced in rendering plants. Rendering plant effluent streams thus contain varying amounts of non-recovered proteinaceous matter diluted with wash water.
Within the present state of the art, diverse coagulation methods are available for removing proteinaceous and other matter from the rendering plant effluents. These methods include steam coagulation and lignin treatments. Alternatively, conventional coagulation chemicals are applied in low dosages to flocculate, coagulate and precipitate rendering plant wastes.
However, these prior methods have very significant drawbacks especially when it is desirable to reuse the high protein precipitant. Lignin treatment, for example, has very unfavorable stoichiometry which results in a product containing 30 or more percent lignin. The introduction of these large amounts of lignin interferes with the economics and the overall efficiency of the utilization of the precipitant as feed. Steam coagulation and pH adjustment are similarly impractical as the sole treatment method due to unfavorable cost effectiveness. Finally, the use of low dosages of polyelectrolytes (5-100 range based on weight) to coagulate rendering plant wastes has been found to be effective only where the effluents contain concentrations of proteinaceous matter significantly below 1%.
Where rendering plant effluents contain 1% or more proteinaceous matter, the traditional treatment methods have been found to be especially ineffective. The usual dosages of polyelectrolytes, for example, have been found to be almost totally ineffective in treating these high protein level effluents. I have now discovered that certain polyelectrolytes at heretofore unprecedented concentrations will surprisingly and efficiently flocculate, agglomerate and precipitate rendering plant effluents containing greater than 1% by weight proteinaceous matter.